This feature request is working its way through the backlog queue. No new details are available yet.
As stated in the last update, the ability to use multiple Teams accounts at the same time is being implemented in stages for Desktop. Faster tenant switching functionality on the Windows client has been rolled out to the public ring fully, and Mac will begin rolling out soon. Work is in progress on cross-tenant notification improvements, and support for multiple accounts on desktop will follow. We’ll keep you posted!
Note: The ability to use multiple Teams accounts at the same time is supported on iOS & Android today.
Alex & the Teams team
This feature item is still in the works. We will keep you posted as we have new info from the feature team.